1. Field of the Invention
The present invention relates to a fuel cell system for a moving object that enables an operation of a fuel cell in a range of overheat not occurring in the fuel cell, even when a temperature detection mechanism of a cooling system malfunctions.
2. Description of the Related Art
These years from such a viewpoint of suppressing a discharge amount of carbon dioxide that causes global warming is noticed a fuel cell electric vehicle (FCEV). The FCEV mounts a fuel cell (FC) for generating power by electrochemically reacting hydrogen (H2) and oxygen (O2) in air, supplies the power generated by the fuel cell to a traction motor, and produces driving force.
In this connection, the fuel cell becomes highest in its power generation performance (electromotive force) by a temperature thereof being maintained at a predetermined value (for example, 80 degrees Celsius): if the temperature is too low, the power generation performance lowers; and if too high, there occurs a possibility that a fuel cell main body and instruments (piping, valve, and the like) receive heat damage. Therefore, a technology is known that detects a temperature (cooling water temperature), cooling water amount, and the like of the fuel cell by a water temperature sensor and a flow rate sensor, wherein when each value is deviated from a predetermined range, a controller reduces an output of the fuel cell main body by compensation control (for example, see paragraphs 0020 and 0021 and FIG. 1 of Japanese Patent Laid-Open Publication Hei. 8-195208 (hereinafter referred to as patent document 1)). Meanwhile, the FCEV leads cooling fluid circulating within the fuel cell to an radiator placed at a front area of a vehicle body and performs cooling by running wind (for example, see paragraphs 0037 and 0042 and FIG. 1 of Japanese Patent Laid-Open Publication No. 2003-182379).
However, in the apparatus of the patent document 1, when there occur a malfunction of a water temperature sensor, a disconnection of an electric harness connected to the water temperature sensor, and the like, compensation control based on a cooling fluid temperature results in being not correctly performed and there is a possibility that following problems occur: For example, if the controller recognizes the cooling fluid temperature lower than actual one, an output (power generation current) results in being not limited in spite of the fuel cell temperature being high, and it may happen that an excessive temperature rise occurs in the fuel cell. In addition, if the controller recognizes the cooling fluid temperature higher than actual one, the output is reduced in spite of the fuel cell temperature being an adequate value, and it may happen that the output is gradually reduced and the FCEV results in being unable to run.
Consequently, a fuel cell system is strongly requested that estimates a cooling amount of a fuel cell by a cooling mechanism from a running speed of a moving object and an outside air temperature and sets an upper limit value of a power generation current of the fuel cell based on the cooling amount.